On the pirates I redeemed it on (my level 3 and 4) I kept it. I did not redeem it on my level 50 and 32, as by then they have outgrown the sword. Not to mention that those two pirates have almost full inventories. I suppose its a sword worth keeping if you are under level 25 or so. After that its probably not worth the inventory slot unless you are keeping it for collection sake.

I have it on all my pirates, even my level 50. But only because there might be an update linked to it. If there isn't though, I'll definitely trash it.

There will be an update to it. Recently, there was a Test Server announcement that said that you might wanna keep the Sword of Triton handy for a new update coming soon... Test Server people can try it now! My guess is zombies are coming.